1. Technical Field
This invention relates to an electrostatic chuck.
2. Related Arts
Patent Document 1 proposes an electrostatic chuck shown in FIG. 5 as an electrostatic chuck for attracting and fixing a plate member of a wafer, etc.
The electrostatic chuck shown in FIG. 5 is formed with a plurality of projection parts 102, 102, . . . each having a flat tip face, formed on an attraction and fix face of a dielectric layer 100, and an exit of a coolant gas flow path 104 is opened in a valley part formed between the projection parts 102 and 102.
Further, in the electrostatic chuck shown in FIG. 5, the full face of the attraction and fix face containing the tip end faces, side faces, and valley part faces of the projection parts 102 is ground.    [Patent Document 1] Japanese Patent Laid-Open No. 2003-86664
In the electrostatic chuck shown in FIG. 5, when a plate member 106 is attracted and fixed onto the attraction and fix face of the dielectric layer 100, the plate member 106 and the dielectric layer 100 are in contact with each other on the flat faces formed on the tip faces, and helium as a coolant gas passing through the coolant gas flow path 104 flows out into the valley between the projection parts 102. Thus, heat added to the plate member 106 attracted and fixed onto the attraction and fix face of the dielectric layer 100 can be radiated rapidly.
Further, the full face of the attraction and fix face of the electrostatic chuck is ground and thus when the plate member 106 is attracted and fixed, scattering of particles from the attraction and fix face of the electrostatic chuck can be prevented.
In the electrostatic chuck shown in FIG. 5, however, the full face of the attraction and fix face containing the projection parts 102 of the dielectric layer 100 is ground and thus the manufacturing process of the electrostatic chuck is complicated.
Further, it turned out that the boundary part between the tip face and a side face of the projection parts 102 of the dielectric layer 100 becomes round and the contact area between each tip face and the plate member 106 becomes lower than the design value. It is difficult to predict lowering of the contact area caused by grinding.
By the way, the contact area between the tip face of each of the projection parts 102 and the plate member 106 is important for striking a balance between the attraction force of the plate member 106 and heat removal of the plate member 106 and it is necessary that the contact area does not substantially change before and after grinding.
On the other hand, the grinding is necessary for preventing minute projections of each tip face from scattering as particles when the plate member 106 and the tip faces of the projection parts 102 come in contact with each other.